043  
FXUS02 KWBC 151903  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
302 PM EDT SUN MAY 15 2022  
 
VALID 12Z WED MAY 18 2022 - 12Z SUN MAY 22 2022  
 
...PERSISTENT RECORD-BREAKING HEAT IS LIKELY IN THE SOUTH-CENTRAL  
U.S. THROUGH THIS WEEK WITH ANOMALOUS HEAT EXPANDING INTO THE EAST  
BY THE WEEKEND...  
 
   
..OVERVIEW
 
 
UPPER TROUGHING SHOULD SHIFT OUT OF THE NORTHEAST AS THE PERIOD  
BEGINS ON WEDNESDAY, WITH BROAD RIDGING TO ZONAL FLOW BEHIND  
ACROSS THE REST OF THE LOWER 48. THE PATTERN IS EXPECTED TO  
AMPLIFY LATER IN THE WEEK AS UPPER TROUGHING DIGS IN THE WEST,  
YIELDING COOLER TEMPERATURES AND LOWERING SNOW LEVELS IN A ROUND  
OF PRECIPITATION SPREADING ACROSS THE NORTHWEST. STUBBORN RIDGING  
ACROSS THE SOUTH WILL CONTINUE TO PROMOTE UNSEASONABLY HOT  
WEATHER, WITH THE MOST PERSISTENT AND RECORD-BREAKING HEAT  
CENTERED IN TEXAS AND THE LOWER MISSISSIPPI VALLEY. WARMER THAN  
NORMAL TEMPERATURES ARE FORECAST TO SPREAD INTO THE EAST AS THE  
RIDGE AMPLIFIES AHEAD OF THE TROUGH IN THE WEST, BUT THE HEAT  
SHOULD FINALLY BREAK BY NEXT WEEKEND ACROSS PARTS OF THE SOUTH.  
INITIALLY THE BEST FOCUS FOR SHOWERS AND THUNDERSTORMS AROUND  
MIDWEEK WILL BE OVER THE OHIO VALLEY ALONG A QUASI-STATIONARY  
FRONT, BEFORE PRECIPITATION SPREADS INTO THE NORTH-CENTRAL U.S.  
AROUND THURSDAY AND EASTWARD LATE WEEK. FLASH FLOODING AND SEVERE  
WEATHER ARE BOTH THREATS WITH THIS SYSTEM. SHOWER/THUNDERSTORM  
CHANCES WILL ALSO INCREASE IN FLORIDA LATE THIS WEEK GIVEN  
INCREASING TROPICAL MOISTURE.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
MODEL GUIDANCE REMAINS IN GOOD AGREEMENT FOR GENERALLY ZONAL FLOW  
WITH A COUPLE OF EMBEDDED SHORTWAVES ACROSS THE LOWER 48 TO START  
THE MEDIUM RANGE PERIOD WEDNESDAY, BEFORE AMPLIFICATION LATER THIS  
WEEK AS TROUGHING BUILDS IN THE WEST CREATING RIDGING DOWNSTREAM.  
THE PROCESS FOR BUILDING THIS TROUGH STEMS FROM POTENT ENERGY  
INITIALLY JUST OFFSHORE OF BRITISH COLUMBIA SPILLING INTO THE  
NORTHWEST LATE WEDNESDAY INTO THURSDAY AND PROGRESSING EASTWARD.  
HOWEVER, SOME NOTABLE DIFFERENCES REMAIN REGARDING THE SPLITTING  
OF THIS ENERGY INTO MULTIPLE FEATURES OR MORE CONSOLIDATION, AS  
WELL AS VARIATION WITH AN EMBEDDED UPPER LOW BEING CLOSED AT  
DIFFERENT POINTS/TIMES. RECENT MODEL GUIDANCE INCLUDING SOME OF  
THE 00Z RUNS AND THE NEWER 12Z RUNS HAVE TRENDED TOWARD SHOWING A  
CLOSED LOW AROUND FRIDAY, SEPARATE FROM BUT EVENTUALLY INTERACTING  
WITH A FARTHER NORTH HUDSON BAY UPPER LOW. NAMELY, THE 00Z/12Z  
ECMWF AND UKMET INDICATED A CLOSED LOW, WHILE THE 12Z GFS AND CMC  
TRENDED TOWARD THIS AS WELL AFTER MORE OPEN EARLIER RUNS. 12Z RUNS  
ARE THUS SHOWING BETTER AGREEMENT FOR THE SURFACE LOW POSITION AS  
WELL IN THE UPPER MIDWEST DAY 5/FRIDAY, SO HOPEFULLY FRONTAL  
POSITIONS AND QPF ARE FOLLOWING SUIT. THE SOUTHERN END OF THE  
TROUGH'S PROGRESSION REMAINS SOMEWHAT UNCERTAIN AS DOES THE  
EASTERN SIDE BY AROUND SATURDAY, WITH THE LATTER ISSUE DEPENDENT  
ON INTERACTIONS WITH THAT NORTHERN STREAM LOW. THERE HAS BEEN A  
GRADUAL TREND TOWARD A SLOWER TROUGH AND THUS FRONTAL PROGRESSION  
IN THE NORTHEASTERN U.S. COMPARED TO PREVIOUS FORECASTS. THE 00Z  
CMC APPEARED TO BE ON THE FASTER SIDE. THE UPDATED WPC FORECAST  
USED A BLEND OF THE 00Z/06Z DETERMINISTIC GUIDANCE EARLY IN THE  
PERIOD, TRANSITIONING TOWARD A NEAR EVEN BLEND OF THE  
GFS/ECMWF/GEFS MEAN/EC MEAN BY THE LATTER PART OF THE PERIOD.  
 
   
..WEATHER/THREAT HIGHLIGHTS
 
 
INITIAL RIDGING ACROSS THE SOUTHERN PLAINS AND RISING HEIGHTS  
FARTHER EAST OVER THE DEEP SOUTH WILL PROMOTE A BROAD AREA OF HEAT  
ACROSS MUCH OF THE SOUTHERN U.S. DURING THE PERIOD. THE GREATEST  
AND MOST LASTING ANOMALIES THROUGH THE PERIOD SHOULD BE OVER TEXAS  
(PERSISTING FROM THE SHORT RANGE TIME FRAME) WHERE SOME LOCATIONS  
COULD SEE HIGHS UP TO 15-25F ABOVE NORMAL, WITH NUMEROUS DAILY  
RECORD HIGHS LIKELY. PARTS OF THE SOUTHWEST INTO THE CENTRAL GREAT  
BASIN AND SOUTHERN/CENTRAL ROCKIES CAN EXPECT HIGHS AROUND 10F  
ABOVE AVERAGE ON WEDNESDAY BEFORE A COOLING TREND AS THE DEEPER  
TROUGHING PRESSES INLAND, WHICH SHOULD HELP MODERATE TEMPERATURES  
IN TEXAS BY THE WEEKEND. HOWEVER, WARM TO HOT TEMPERATURES ARE  
ALSO FORECAST FOR THE SOUTHEASTERN QUADRANT OF THE U.S. WITH  
POTENTIAL FOR DAILY RECORD HIGHS, AND WARMER THAN AVERAGE  
TEMPERATURES BY 10-20F SHOULD EXPAND IN COVERAGE ACROSS THE OHIO  
VALLEY TO EASTERN SEABOARD BY LATER IN THE WEEK.  
 
A WARM FRONT LIFTING THROUGH THE MID-MISSISSIPPI VALLEY AND OHIO  
VALLEY WILL PROVIDE A FOCUS FOR MULTIPLE AREAS OF SHOWERS AND  
STORMS/CONVECTIVE COMPLEXES DURING THE MIDDLE TO LATTER PART OF  
THE WEEK. THE INGREDIENTS ARE IN PLACE FOR HEAVY RAINFALL, THOUGH  
THE SPECIFICS OF COVERAGE AND AMOUNTS ARE UNCERTAIN, BUT AT LEAST  
A LOCALIZED FLOOD THREAT IS LIKELY ESPECIALLY IF HEAVY RAIN FALLS  
IN AREAS THAT ARE SENSITIVE TO ADDITIONAL RAINFALL. THEN ORGANIZED  
RAINFALL, HEAVY AT TIMES, IS LIKELY ALONG A FRONTAL BOUNDARY  
THROUGH THE NORTH-CENTRAL U.S. AROUND THURSDAY WITH POTENTIAL FOR  
AT LEAST LOCALIZED FLOOD AND FLASH FLOOD THREATS GIVEN WET  
ANTECEDENT CONDITIONS ACROSS THAT REGION. STORMS THAT COULD BE  
SEVERE ARE FORECAST TO SHIFT FROM THE UPPER MIDWEST INTO PARTS OF  
THE OHIO AND MISSISSIPPI VALLEYS ALONG THIS FRONT THURSDAY INTO  
FRIDAY. ADDITIONALLY, TROPICAL MOISTURE INCREASING ACROSS THE  
FLORIDA PENINSULA LATE THIS WEEK COULD LEAD TO A MORE RAINY  
PATTERN FOR THE SUNSHINE STATE.  
 
AFTER A COUPLE OF INITIAL FRONTS CROSSING THE NORTHWEST, THE MAIN  
WELL-DEFINED FRONT AHEAD OF THE DEEPENING TROUGH WILL BRING  
UNSEASONABLY COOL TEMPERATURES TO THE NORTHWEST AND EXPANDING INTO  
THE NORTHERN ROCKIES AND HIGH PLAINS BY LATE WEEK. THIS WILL ALSO  
PROVIDE SUPPORT FOR A NOTABLE ROUND OF PRECIPITATION, WITH  
LOWERING SNOW LEVELS IN THE CASCADES TO NORTHERN ROCKIES AS THE  
WEEK PROGRESSES, WITH SOME CHANCE OF SNOW EVEN INTO NORTHERN PARTS  
OF THE HIGH PLAINS, THOUGH WITH VERY LOW CONFIDENCE AT THIS POINT.  
 
TATE/SANTORELLI  
 
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, EXPERIMENTAL EXCESSIVE RAINFALL  
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES ARE  
AT:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 

 
 
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